Project Summary The burden of Alzheimer?s Disease (AD) takes a significant toll on the patient, their families and communities, and the healthcare system. Without effective intervention and prevention strategies, the prevalence of AD is expected to more than double over the next 30 years. It is critical to identify protective factors that can be leveraged for more effective prevention before the onset of the disease. Conscientiousness is a personality trait that is associated consistently with better health outcomes, which extends to dementia: Conscientiousness is one of the most replicated psychological factors that is protective against cognitive impairment. Most work on Conscientiousness has focused on its agentic aspects (e.g., self-control, achievement striving). Conscientiousness, however, has a distinct interpersonal component that is often overlooked in the relation with health in general and cognition in particular. Yet, Interpersonal Conscientiousness, defined as either responsibility or dutifulness, is protective against dementia, an effect that is independent of the agentic components of this trait. The objective of this proposal is to identify the mechanisms through which Interpersonal Conscientiousness leads to better cognitive outcomes. The proposed research will leverage longitudinal data from the Health and Retirement Study (HRS) and pair it with new data collection in couples on ambulatory cognition to identify the pathways through which Interpersonal Conscientiousness protects against cognitive decline over a decade (HRS) and daily cognition (new data) across a critical period of the lifespan ? midlife and the transition to old age (ages 40-70). In both samples, we will test clinical/physiological (e.g., fewer chronic diseases, lower inflammation), behavioral (e.g., physical activity, active engagement), psychological (e.g., greater purpose in life, less stress), and relational (e.g., greater support, less loneliness) factors as mechanisms of the relation between Interpersonal Conscientiousness and healthier cognitive outcomes. In addition, we will examine actor and partner effects to test whether the protective effect of Interpersonal Conscientiousness extends to the partner. This work will lead to new knowledge on how Interpersonal Conscientiousness promotes healthier cognitive aging and point to new prevention and intervention targets for promoting healthy cognitive aging in across adulthood.